of the Pdrall'eUsm bfCbhtMporaneous Lines of Elevation. 121 



intervals through a long period of ages : thus in the example 

 cited, of the transition rocks of the Ardennes and the coal- 

 fields of the jNIeuse, it is evident that all the rocks anterior to 

 the new red have been violently convulsed, and those subse- 

 quent have been little, if at all thus affected. But who shall 

 say that all this disturbance was produced at one blow? This 

 point, indeed, admits of determination by carefully examining 

 whether a general conformity does or does not pervade the 

 whole of the disturbed series; — for if there be anything like 

 general interruptions in that conformity, every such interrup- 

 tion would clearly indicate a distinct aera of convulsion. Now, 

 d'priori, it should certainly appear that the idea of a series of 

 successive convulsions seems most conformable to the only 

 analogy presented by actual causes, the operations of volcanic 

 forces ; and the careful and minute examinations which would 

 be necessar}' to ascertain every interruption of conformity in 

 the strata of the disturbed districts have hitherto scarcely in 

 any single instance been accurately made. 



Having thus candidly avowed the difficulties and obscurities 

 which hitherto overcloud this important branch of geolo- 

 gical inquiry, we may proceed to state the few data on the 

 subject which are as yet to be considered as tolerably ascer- 

 tained, so far as the geology of this Island is concerned ; and 

 in doing this we shall find it most convenient to begin with 

 the convulsions of the most recent order which have been 

 here observed ; those, namely, which have occurred during the 

 period of the tertiary formations. The tertiary formations, 

 and the chalk on which they rest, have participated in the 

 general elevation of all the secondary strata of the Island, of 

 ■which the general line of bearing is from N.E. to S.W., but 

 there is no appearance whatever of this elevation having been 

 the result of any violent sudden or single convulsion ; on the 

 contrary, everything indicates that it was a gradual, gentle, 

 and protracted upheaving (to borrow a German term), con- 

 tinued without interruption during the whole period of the 

 formation of all these strata; or perhaps some persons may be 

 inclined to refer it rather to an equally progressive depression 

 of the basins of the surrounding ocean : as all the phfenomena 

 simply indicate a relative change of level, (hey will admit an 

 equally ready explanation on either hypothesis. We may ob- 

 serve a very general tendency to parallelism between this line, 

 (although the residtof a cause certainly continuing to act in 

 the same direction in the tertiary epoch,) and the earlier and 

 more violent convulsions which we shall hereafter find to have 

 aflfectctl the older carboniferous strata before the deposition 

 Third Series. Vol. I. No. 2. Au". 1832. R 



